Pharmaceutical packaging, such as sealed pockets, blister strips, disks and packs, for doses of medicaments or pharmaceutical compositions in the form of powders, tablets or capsules are well known in the art. As applied in dry powder inhaler technology, the pharmaceutical packaging (e.g., blister strips) generally comprise a base having cavities, pockets or open “blisters” adapted to receive a pharmaceutical composition (e.g., inhalable dry powder), a lid that encloses the opening of each cavity or blister, and an adhesive or bonding layer disposed therebetween to effect a seal.
It is further well known that pharmaceutical compositions, and in particular, inhaled dry powders, must be maintained in a hermetic environment to maintain a high degree of physical stability in particle size. Only particles having a specific narrow range of aerodynamic diameter size will deposit in the desired location in the pulmonary system. For instance, a particle for local treatment of respiratory conditions such as asthma will have a particle size of 2–5 μm. Particle to particle agglomeration, shifting the particle size outside of this range, will cause the particle(s) to deposit away from the target region of the lung. Such agglomeration has been associated with moisture ingress into the pharmaceutical packaging (i.e., blister). Particle sizes, either in aerodynamic or geometric measures, referred to herein relate to a particles effective particle size. Effective particle size denotes the apparent particle size of a body without distinction as to the number of individual particles which go to make up that body, i.e., no distinction is made between the single particle of given size and an agglomerate of the same size which is composed of finer individual particles.
Similarly, exposure of a pharmaceutical composition to high temperatures can, and in many instances will, undermine the stability and, hence, efficacy of the pharmaceutical composition. Accordingly, it is important to closely monitor the environmental conditions to which a pharmaceutical composition is exposed to ensure that the pharmaceutical composition's physical and chemical stability has not been degraded.
Various prior art sensing devices and systems have been employed to monitor environmental conditions proximate pharmaceutical packaging and/or compositions. However, in general, the noted devices and systems are not suitable for monitoring environmental conditions “inside” pharmaceutical packaging, and in particular, blister packs.
For example, U.S. Pat. No. 5,739,416 discloses a surface acoustic wave (SAW) device that detects the presence of moisture. Surface acoustic waves are transmitted through a delay path that is attenuated by the presence of condensation. Unfortunately, SAW devices are extremely sensitive to temperature, pressure, and vibration or other physical conditions. Compensating for these factors increases the complexity and cost and generally renders SAW sensors unsuitable for use in pharmaceutical packaging.
There are also numerous drawbacks associated with the magnetoacoustic sensors disclosed in Jain, et al., “Magnetoacoustic remote query temperature and humidity sensors” Smart Mater. Struc. 9(2000), pp. 502–510. The most significant drawback is that the disclosed sensors are too large for incorporation into conventional pharmaceutical packaging and cannot be easily reduced in size, since size reduction substantially changes the resonant and interrogation frequencies, as well as the amplitude of the generated signal. Further, the mass changing, moisture sensitive materials disclosed by Jain, et al. would yield unsatisfactory results since they do not exhibit enough mass change when incorporated with a smaller sensor.
It is therefore an object of the present invention to provide a highly efficient, cost effective means for determining environmental conditions within a multitude of pharmaceutical packaging and, in particular, pharmaceutical packaging having limited internal space.
It is another object of the present invention to provide a microelectromechanical (MEMS) system and method for determining at least one, preferably, a plurality of environmental conditions within pharmaceutical packaging.
It is another object of the present invention to provide a remote sensor system and method for determining the temperature profile within pharmaceutical packaging.
It is another object of the present invention to provide a remote sensor system and method for determining the humidity profile within pharmaceutical packaging.